506 PROFESSOR GREGORY ON 



(Since this paper was read, I have ascertained that the peculiar plates above 

 mentioned in Apr. pusilla, and in Apr. plicata, occur also in this species. I had 

 overlooked them, from their being very narrow. They rise from the inner margin 

 of the valves, as seen on the F.V., from two points a short distance from the ex- 

 tremities. Their convex margin extends in the middle just beyond the constric- 

 tion. They are so narrow as to be readily overlooked, but are quite distinct, 

 and appear to be thicker at the outer or convex margin than at the inner or plane 

 one. There is even some appearance of a second plate in each valve, rising from 

 the same line, as that just mentioned, but apparently extending in a plane at 

 right angles to the surface of the valve, so that, in the F.V., it is seen foreshortened, 

 and appears as a dark line. But I am not yet satisfied about this second plate. 



The plates first named constitute a very peculiar feature, both in this species, 

 and in the two previously described. We shall see the same structure still more 

 developed in another species, a very remarkable one, namely, Apr. maxima.) 



The form represented in fig. 59 c, I am satisfied belongs to this species ; but I 

 do not quite understand its relations. It is of an elegant rhombic-lanceolate 

 form, with two curve-lines on each side, which at the middle bend inwards, to 

 join a strong stauros, interrupting the median line, and at the ends coalesce with 

 the margin. The whole valve is marked with fine parallel striae, except the 

 stauros. This form, as will be seen, differs considerably from the usual S.V., (fig. 

 59 b), which latter often occurs with the longitudinal lines in it much more curved 

 than in the example figured. Can the lateral lines in fig. 59 c be the outer mar- 

 gins of the two plates, above described, or perhaps of those suspected to lie in a 

 different plane ? 



This species first occurred to me in the Glenshira Sand, and I figured the S.V. 

 as Apr. vitrea, /3 ? in my first plate of that deposit (Mic. Jour., vol. in., pi. iv., 

 fig. 14, the larger of the two figures, which shows the curved lines above alluded 

 to, with a third line to the side) ; and the F.V. in my third plate ( Trans. Mic. 

 Soc, vol. v., pi. i., fig. 39). But the former had not the striae, and the latter was 

 from a very inferior specimen, and, besides, did not show the peculiar plates. 

 I have therefore figured both views here from good specimens, which are frequent 

 in Mr Miles's Corallina gathering from Corriegills, near Lamlash Bay. It is at 

 once distinguished from Apr. diclyma by its much more elegant form, and by 

 being twice as long. The S.V., also, is quite different. I am informed by Dr 

 Greville that he finds this form abundantly, even predominating, in a dredging 

 or gathering from nearly the same locality, which he made early last summer. 



60. Amphiprora obtusa, n. sp. PL XII., fig. 60. Form of F.V. linear, broad, 

 with rounded ends, slightly incurved in the middle. The termination of the 

 middle space projects a little beyond the general curve of the apices. The inner 

 margin of the striated part of the valve is gently and gracefully curved, forming 

 two concave lines towards the middle, which meet in a point of the inner margin 



